>>Dr. Ketchum: So in this part we’re going to focus on immune responses in health and disease.
So to begin with, we want to look at naturally versus artificially acquired immunity. So
when you think about natural immunity, think about the fact that you’ve somehow been
exposed naturally to an antigen. If it’s artificial immunity, then you’ve been injected
with something and that injection has caused you to mount an immune response.
Okay, now regardless of whether it’s natural or artificially acquired immunity, you have
two different forms. There’s passive and active. So what we’re going to do is go
through each of these first. So we’ll begin with naturally acquired immunity. So let’s
look at the passive form first. So you have mom who gets exposed to the invader. So think
about the invader as the antigen, and then mom produces antibodies to that antigen. So
now mom gives birth to you. Okay, so when mom gives birth to you, she passes her antibodies
on to you, the newborn child. So I want you to illustrate on the graph below how you think
the level of antibody would change in the newborn over time. So I’ll give you a few
seconds to do that. If you want to pause the video for a moment to have more time to think
about how the antibody level would do over time, please do so.
What we’re going to do—and we’re going to think, “Okay, let’s look at our axis.”
Time is on the X-axis and antibody level is on the Y-axis. So when mom gives birth to
you, your antibody level is going to be high at birth, right? So you can about time zero
as birth; so that antibody level will be high. Now you have never been exposed to this antigen,
so your body has no memory cells. It has no B cells to this particular antigen. So over
time, that antibody level is going to drop. Antibodies don’t live forever. So that’s
a passive naturally acquired immunity. It’s naturally acquired because you were naturally
given those antibodies from mom because she was exposed to the antigen. Now we move on
to the active naturally acquired immunity. So an active naturally acquired immunity—
now we’re going to leave mom behind. We’re not going to worry about mom and pregnancy
any more, now we’re going to think about you yourself.
So you’ve acquired the invader, so you’ve been exposed to the antigen, and then you
make antibodies to the invader. So if you survive, this is actually the best form of
immunity is to get exposed to it and build up your own immunity to it. So now what I
want you to do is to illustrate on the graph how your antibody level would change over
time once you’ve been exposed to this particular antigen. So again, if you’d like to take
a moment to do this, pause the video and then play the video again and you’ll get the
answer. Your antibody level is going to start off low. We’re going to start off at time
zero where you don’t have any antibodies yet to this antigen because you haven’t
been exposed. Once you become exposed, your body’s going to produce those antibodies.
Remember that the first response, the first time you’ve been exposed to the invader,
it’s going to take you seven to 10 days to make antibodies. So your level goes up
and it kind of plateaus, right?
Now if you get exposed for a second time, then this antibody, do you think it will go
up or go down if you get exposed to the same antigen for a second time? Hopefully you said
it would go up,. So then eventually this level plateau, and then eventually it’s going
to start to decline a little bit, okay? Because again, those antibodies are not going to survive
forever. However—this is the catch—in active immunity, you have memory cells. So
if you are ever exposed again, you can easily and very quickly make more antibodies. Remember
in the passive form, you do not have any memory cells or plasma cells for that matter, because
you weren’t actually exposed to the antigen.
Okay, so blood types are actually a form of natural immunity. And in lab, you have already
experienced these various blood types. So be sure that you can go through and you understand
how blood types are a form of natural immunity and all the information that we did in lab
is the same information that’s here. Be sure you know this material. If you need some
help, please come see me. Okay, so now we move on to artificially acquired immunity.
So the same thing holds true. We have two different types—we have passive and we have
active. So let’s look at passive first.
So in passive, there’s a serum containing the antibody and you’ve been injected with
it. So you’ve been injected with an antibody. You’ve never been exposed to the antigen,
but you’ve been injected. So now please pause the video and illustrate on the diagram
how you think your antibody level would change over time if you were injected with the antibody.
So your antibody level would start off high, correct, because you’ve been injected with
it. And then over time it would decrease, okay, because again, you haven’t actually
been exposed to the antigen. So you would never make any plasma cells, you would never
make your own antibodies, and you would never make any memory cells. Then there’s the
active form. Active is where you’ve actually now been vaccinated, and you’ve been vaccinated
by the nonvirulent form.
What this means is this is supposed to be the form of the antigen that does not make
you sick, but it does stimulate the production of antibodies by your body. So you’re going
to man an immune response and you’re going to make antibodies. So now indicate on the
graph when the first vaccination and when the booster was given, and then why should
a booster be given. So the first vaccination here, and then over time, we noticed that
the antibody level dropped and then it went back up. So the point at which the antibody
level went back up must be where you were given a booster. So notice how much more the
antibody level increased when you gave a booster. So it’s a very good thing to give a booster,
okay? Your antibody level goes up that much more and you produce more memory cells.
Now we also have immune dysfunctions and one of those are allergies, which a lot of us
suffer from. So allergies are actually hypersensitivity reactions. And when you have a hypersensitivity
reaction, you’re going to have an increase in immunoglobulin E. Now the most serious
consequence of an allergic response is the fact that when we have IGE antibodies being
produced, that can cause your mast cells to secrete histamine.